The invention relates to a two-mass flywheel to be disposed in the drive line of a motor vehicle driven by an internal combustion engine.
Known from DE-A-37 21 712 is a two-mass flywheel having two flywheels which are mounted to rotate relatively to each other and which are coupled to each other in torsionally elastic manner by a torsional vibration damping means. While the first of the two flywheels is fixed on the crankshaft of the internal combustion engine, the second flywheel carries a friction clutch via which the gear mechanism which is on the downstream side in the drive line can be isolated from the internal combustion engine when starting up and changing gear.
Where the prior art two-mass flywheel is concerned, the first flywheel contains a passage circularly enclosing the pivot axis and in which a plurality of comparatively long coil springs are disposed and each of which is independently controlled by end shoes of the torsional vibration damping means. The coil springs are connected in parallel with one another but by reason of their considerable length they permit a comparatively wide angle of relative rotation between the two flywheels. In order to reduce friction, the passage is at least partially filled with a viscous lubricant.
By reason of their great length, the coil springs of the prior art two-mass flywheel are, during operation, by virtue of the compression and centrifugal force, pressed against the inner wall surface of the first flywheel which radially outwardly defines the passage. Due to the friction of the coil springs against the inner wall surface, even at low rotary speeds and with minimal angles of rotation of the flywheels in respect of each other, a controllable but high level of basic friction results.